Traditionally, spectrum analyzers have had minimal triggering capabilities. For instance, a common display on a spectrum analyzer, of power-versus-frequency, was normally untriggered. Recently, as spectrum analyzers have converted to digital acquisition technology, more advanced triggering has been introduced.
With today's communication standards, frequency hopping and phase modulation are becoming more prevalent. In frequency hopping applications, the power of a radio frequency (RF) signal is constant as the frequency changes. This renders the traditional power trigger useless because there is no change in power to trigger on. Users need to be able to trigger (and thus, acquire data) when a particular frequency is reached or when a particular phase value is reached. Conventional approaches to solve these problems in spectrum analyzers, such as via a frequency mask triggering approach, can discourage users for a variety of reasons. For instance, the time resolution is too granular to achieve desired trigger performance in many applications. In addition, the ability to resolve closely spaced frequency components can be limited with the frequency mask trigger.
Moreover, RF signals often include pulses or RF “bursts” in which information is transmitted during a burst of activity, followed by periods of inactivity or noise. This can lead to false and inaccurate triggering. Current techniques do not provide a trigger that easily isolates the frequency or phase event of interest and then trigger on and/or capture only the data that is of interest. If the event of interest occurs only rarely (e.g., once per day or week), it is impractical to store enough acquisition data to ensure the event can be seen and analyzed.
Accordingly, a need remains for a more flexible instrument and method for generating triggers for frequency and phase information.